Performance and Race Carburetors - When you want to go beyond mild street performance and into the realm of more serious power and perhaps competition, carburetors with mechanical secondaries and two instead of one accelerator pump become a more effective solution. These so-called “Double Pumper” carburetors give you more consistent, precise, and tunable secondary actuation, along with a larger shot of fuel on acceleration, to minimize bog when the throttle blades are opened abruptly. Many of Holley’s Performance and Race Carburetors also have billet metering blocks, which have better resistance to fuel corrosion and lower chance of porosity in the fuel block. But, at the same time, most of Holley’s Performance and Race carburetors still have a choke system, to make cold starts easier for street use.